A planetary transmission for a bicycle and a method of obtaining higher riding speed due to the interaction between transmissions are based on the experimental data of conversion of gravity into mechanical rotational energy (approved by U.S. Pat. Nos. 5,667,038; 5,921,133A; 6,363,804 B1; 6,601,478 B2) and experimental data of riding new type of bicycle having planetary transmission (approved by working model since 1999 and two prototypes since 2002).
The main difference between the regular and the new type of bicycles is in their pedals' system.
A regular bicycle has a balanced pedals' system with two similar pedals freely rotated around their axes under the foot's muscular energy.
The new type of bicycle has an unbalanced pedals' system with two different pedals. One pedal is a regular one and freely rotates around its axle under the foot's muscular energy.
The other is different in terms that it rotates around its axle not only under the foot's muscular energy, but also under the earth gravity in the positive zone of rotation and under the inertial energy supported by foot's muscular energy in the negative zone of rotation.
The gravitational pedal carries out two functions:                to transmit the driving power from the foot's muscular energy to a drive wheel of a bicycle        to transmit the driving power from the foot's muscular energy together with gravitational energy for its recirculation by means of inertial energy, appearing in a negative zone of rotation!        
It can be proven by various tests, and gravitational pedal makes it much easier (spending less energy) to ride a bicycle.
The gravitational pedal together with the planetary transmission (FIG. 1, FIG. 2A. Parts # 4s;5;5A) makes it possible to ride with higher speed of about 35 MPH (average bicyclists speed is of 15-17 MPH) spending the same muscular energy.
This idea can be a first step towards the production of a faster and more efficient engine systems.